1. Technical Field of the Invention
The present invention relates to a filter used for image display devices such as a plasma display panel.
2. Description of the Related Art
In image display devices such as a plasma display panel, color images are usually displayed by emitting lights of three primary colors of red(R), green (G) and blue (B) in combination, however, there exists a problem of deterioration in contrast and color reproducibility of an image by deterioration of color purity due to the presence of unnecessary lights other than three primary colors. For example, in a plasma display panel using neon-xenon as a rare gas, it is known that visual light emission of so-called neon-orange is a cause of deterioration in color purity (Television Institute Journal, vol. 48, no. 9, pp. 1098-1101, 1994).
As one method for solving such problems, there are various methods suggested absorbing unnecessary lights using a light selective absorption filter, and for example, JP-A-Nos. 2000-43175, 2000-284116 and 2001-13317 suggest an optical filter having a layer containing various dyes as a filter for an image display device such as a plasma display panel.
However, when these conventionally filters are used, unnecessary lights, particularly, lights having wavelengths near 580 nm show insufficient selective absorption and emits fluorescent light, accordingly, contrast and color reproducibility of an image are not satisfactory. Further, since absorption of an unnecessary light lowers and color tone thereof changes by use for a long time, durability is not satisfactory.